As an important type of ocean pollutants, persistent organic pollutants (POPs) can persistently present in marine environment, and will generate harmful effect for the health of marine organisms and human being by accumulation of food chain. High-molecular-weight polycyclic aromatic hydrocarbons (HMW PAHs) should be considered as one type of the most commonplace and important POPs. Due to the characters of high toxicity, persistence, bioaccumulation, lipophilia-hydrophobicity and hardly degradable, HMW PAHs have the effect of tri-genicity (carcinogenicity-mutagenicity-teratogenicity) and genotoxicity, and pose great threat to the marine ecological environment and human health.
Some researches indicated that, microbial degradation is one of the major pathways for removing HMW PAHs from marine environment. Since successfully applied in the bioremediation of the coast, which was polluted by the oil spill accident, in Alaska (USA) in the 90s of the twenty-century, the environment-friendly remediation technology is increasingly valued by scientists and governments of many countries.
The obligate hydrocarbonoclastic bacteria (OHCBs) are very particular microorganisms in marine environment, which have the characters as follows: firstly, high specific surface area, by which the bacteria are capable to adapt the low-nutritional condition of marine environment; secondly, the preference in hydrocarbon compounds degradation, that is, they use hydrocarbons as their sole carbon sources, wherein some of them even cannot use simple organic carbons, such as glucose; thirdly, highly efficiency and broad-spectrum catalytic activity, that is, they present the high degradation rates for different hydrocarbon compounds, such as typical HMW PAHs. The bacteria which have been reported include Alcanivorax, Cycloclasticus, Marinobacter, Marinobacterium, Neptunomonas, Oleispira, Thalassolituus and so on. Wherein, Cycloclasticus strains uniquely possess the capacity of degrading HMW PAHs, and studies show that the rates of degrading HMW PAHs can be further improved by the synergic effect between Cycloclasticus strains and other strains. There is a good prospect for the application of Cycloclasticus strains and its microflora in the remediation of marine environment which has been polluted by POPs (such as HMW PAHs). But, due to the unique growth characters of Cycloclasticus strains which are different from terraneous bacteria, the isolation of bacterial strain with high activity is quite difficult.